I'd like to start out by saying that I do not know squat about an AR15 or its mechanics at all!!!!! I am strictly blued steel, bolt action and walnut stock shooter. The closest I have come to an AR is a Ruger 10-22. I posted about a week ago asking for some help with an AR build for my son for a Christmas present. I got a lot of great and positive feedback, did a lot of research and came up with what I believe good parts for an AR built. I've heard him rant about the Proof Research barrel so it's a 16 inch, Proof Research barrel, .223 Wylde chamber, 16 inch mid barrel (?) and a Seekins adjustable gas block. I know there are lots of opinions on this forum, and......also a wealth of information!!! Now I am looking for some input on a trigger system and a muzzle brake for this rifle. The rifle will be used to shoot steel out to 300 yards, and he'll probably start to work in getting his groups down as small as possible. And if possible I'd like to get them both for around the $500 budget. Thank you for any input.